Steam system for manufacturing salt and the like



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STEAM SYSTEM FOR MANUFACTURING SALT AND THE LIKE. APPLICATION FILED NOV- 23, 1918.

1,391,811. e Sept 27,1921.

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STEAM SYSTEM FOR MANUFACTURING SALT AND-THE LIKE. APPLICATION FJLEB NOV. 23, 191's.

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CHARLES LEWIS WEIL, OF PORT HURON, MICHIGAN; ELLA S. WEIL, ADMINIS- TRATBIX 0F SAID CHARLES LEWIS WEIL, DECEASED.

STEAM. SYSTEM FOR MANUFACTURING- SALT AND THE LIKE.

Specification of Letters Patent-a Patented Sept. 27, 1921,

Application filed November 23, 1918. Serial No. 263,895.

To all ii /20m 2'15 may concern Be it known .that 1, CHARLES L. \VEIL, a citizen of the United States, and resident of Port Huron, in the county of St. Clair and State of Michigan, have invented new and useful Improvements in Steam Systems for Manufacturing Salt and the like, of which the following is a specification.

T his invention relates to a steam or vapor system and more particularly to a steam system for manufacturing salt and the like, the present invention being applicable, 6. 9., to salt making systems of the character disclosed in my former Patents No. 1,261,331 and No. 1,273,208.

In the manufacture of certain products it is desirable, for commercial reasons, to vary the output. For example, the demand for salts of various grades varies throughout the year, thus making it necessary for the manufacturer either to maintain a constant output and store the excess output during the dull seasons, to be sold during the active season, or to vary the output in accord with the varying demand. The first method is costly for the reason that it requires large warehouses and rehandling the product, but heretofore it has usually been resorted to for the reason that the known systems are not adapted to be varied in output economically.

()ne object of the present invention is to provide a method and apparatus for manufacturing salt and the like, which will permit an economic variation of the output without imposing an undue first-cost of in.- stallation and without entailing much time or labor in adjusting to different outputs and without rendering it necessary to leave much if any apparatus idle during periods of reduced output. Another object of the invention is to provide a method and appa ratus for re-utilizing the exhaust steam or vapor in evaporation systems such as saltmaking systems, distillation systems, and other steam systems, such as a power plant comprising a prime mover. Still another object is to avoid a decrease in efficiency as the output is decreasedand indeed to attain an increasing efficiency as the output decreases.

Heretofore, in making salt and the like in closed evaporators, it has been common to employ a series of evaporators and connect the evaporators in series so that the vapor or steam exhausted from one evaporator is fed to the next evaporator, the exhaust steam from-the second evaporator being conducted to the third evaporator, and so on to a condenser. In such systems the output may be regulated to a certain degree but the initial cost and the subsequent maintenance of a system employing a series of evaporators is excessive, and there is no way-of controlling the economy of the systems throughout variatlons moutput except possibly by means of comphcated arrangements of pipes and valves. By the present invention a plurality of evaporative effects may be obtained with a single evaporator, and the economy of the system may be controlled throughout varymg output.

In one aspect the present invention involyes a method of controlling the evaporative effect in the evaporator which comprises raising the pressure of a portion of th steam exhausted from the evaporator, returning said steam to theevaporator at the raised pressure and regulating the exhaust steam returned to the evaporator so as to control the amount of exhaust heat returned to the evaporator. The exhaust steam may be regulated either in quantity or in quality or both, as by varying the amount of exhaust steam returned to the evaporator, or varying the pressure or degree of superheat, or both. In order to compensate for heat losses in the system it is of course necessary to supply energy to the system. Such energy is preferably supplied in the form of live steam and thelive steam is employed to raise the pressure of the exhaust steam, preferably by ejecting the live steam into the exhaust steam and thus producing amixed steam at a pressure intermediate the pressure of the live steam and exhaust steam.

In another aspect the invention involves means for performing the aforesaidmethod. A cardinal feature of said means comprises a steam duct connecting the steam outlet of the evaporator with the steam inlet so that the exhaust steam issuing from the evaporator may be returned thereto, together with means for raising the pressure of the exhaust steam in transit fromv the outlet to the inlet. My preferred means for raising the pressure of the exhaust steam comprises one or more steam ejectors deriving live steam from a suitable source. When employlng a plurality of ejectors a series of steam loops is preferably interposed between the source of 11% steam and the evaporator with an e ector in each loop, the ejector in the first loop being connected to the source of live steam, the last loop being connected at its opposite ends to the inlet and outlet respectively of the evaporator, and each intermediate loop being connected at one end to the e ector in the next succeeding loop and at 1ts other end to the next succeeding loop at a point in advance of the ejector therein.

In one embodiment of my improved system, a series of chambers are interposed between the source of live steam and the evaporator with a plurality of steam ducts connecting the source, chambers and evaporator together so that live steam is conducted through the chambers successively in one direction and exhaust steam is conducted successively through the chambers in the other direction, the steam ducts includin a duct for feeding steam from one of the chambers to the evaporator, and a plurality of ejectors are arranged respectively to eject steam from each chamber into the steam entering the next chamber of lower pressure so as to raise the pressure in the next chamber of lower pressure...When employing such chamber together, with a series of loops as above describedthe chambers are connected betweensuccesslve-loops and serye to connect the loops together. The chambers may comprise either elements distinct from the loops or portions of the steam ducts constituting the loops.

Various adaptations and modifications of my invention will be evident from the following detailed description of certain specific embodiments of the invention and from the accompanying drawings, in which- Figure 1 is a diagram illustrating one application of the invention;

Figs, 2, 3 and 4 comprise a set of diagrams illustrating one form of my new method; and

Figs. 5, 6 and 7 com rise a set of diagrams illustrating another i drm of my improved method.

The particular embodiment of the invention illustrated in Fig. 1, comprises a plurality of sets of apparatus which may be employed singly, or in series as shown in the figure. The set of apparatus at the righthand side of the figure comprises a steamoperated device D in the form of an evaporator, a source of steam S, and a series of chambers C C and C intermediate the source of steam S and the evaporator D. The source of steam S, evaporator D and chambers C,, 0,, and C are connected. together by a series of steam ducts 1, 2, 3, 4;, 5, 6 and i. In the ducts 3, 5 and 7 are steam ejectors E E and E respectively, connected to the steam ducts 1, 2 and 4:. The source tion is of the-ordinary type com rising upper and lower liquid spaces 8 an 9 connected together by a plurality of pipes 10, the space in the central portion of the evaporator surrounding the pipes 10 constituting a heating chamber to which steam is supplied for the purpose of heating the contents of the evaporator. After the steam supplied to said heating chamber has iven up a part of its heat it is exhausted hrough duct 0 to the atmosphere or to a condenser. The liquid level 11 preferably stands intermediate the top and bottom of the upper compartment 8. An exhaust duct 12 leads from the steam chamber C and this duct may lead either to a condenser, a prime mover, another evaporator system, or to any other steam system, to be re-utilized.

Assuming that the source S supplies steam at a. pressure P and that vapor is produced in the evaporator at the pressure P the operation of the system above described is as follows :-The steam passes off from the evaporator D through duct 7 at pressure P and is raised to a pressure P in chamber C by ejector E deriving steam from duct 4: at a pressure P produced in a manner which will presently be described. Part of the steam in chamber C is returned to the evaporator through duct 6 at the pressure P and part of the steam in chamber C, is fed to chamber C through duct 5. The steam passing through duct 5 is raised to a pressure P in chamber C by means of ejector E deriving steam through duct 2 at pressure P, from chamber C,. Part of the steam fed into chamber C at pressure P is fed through duct 4 to ejector 111 as described and the rest of the steam is fed through duct 3 to the chamber P,,. The steam entering chamber C, through duct 3 is raised to a pressure P, by ejector E deriving steam from the source S through duct 1. Part of the steam supplied to chamber P at pressure C, is fed through duct 2 to ejector E as described and the remaining steam is exhausted from chamber C, through duct 12. The ejectors E E and E are preferably adjusted to produce pressures in chambers C C and G which form a geometrical progression with the ressures in the evaporator D and source 2.

bus if the source S supplies steam at a pressure of 32 pounds and the evaporator produces a vapor at 2 pounds the pressures P and P, in the chambers would be of the order of 4, 8 and 16 pounds respectively (all pressures herein referred to being absolute pressures).

The operation of the system above described may be made clearer by considering a concrete example of certain proportion of steam fed through the respective chambers and ducts, it being understood that the following is merely one concrete example, and that other proportions may be employed by suitablyregulating the ejectors, by throttling the ducts, by exhausting steam from either the chamber C or chamber 0, instead of from. the chamber C or in other ways, as will be apparent from subsequent descriptions herein.

One pound of'steam passing from evaporator D through duct 7 at pressure P may be raised to pressure P in chamber C by means of one pound of steam issuing from ejector E, at pressure P The two pounds of steam thus supplied to chamber C, at pressure P, may be equally divided between the ducts 5 and 6, one pound passing to the evaporator D to be re-utilized in heating the contents of the evaporator and the other pound passing to chamber C The pound passin to chamber C may be raised to pressure 3 by one pound of steam issuing from ejector E at pressure P,. The two pounds of steam thus supplied to cham her (3,- at pressure P, may be equally divided-between the ducts 3 and 4:, one pound passing to ejector E, to raise a pound issuing from evaporator D at pressure P, to pressure P as described, and the other pound passing to chamber C,. The pound of steam passing through duct 3 may be raised to pressure 'P, in chamber C, by one pound of steam issuing' from ejector E, at pressure P The two pounds of steam in chamber C, may be equally divided between the ducts 2 and 12, one pound passing to ejector E to raise a pound of steam passing through duct 5 from pressure P to pressure P, as described, and the other pound being exhausted through duct 12 either to a condenser, to another system similar to the one described, or to any other device adapted to utilize steam at pressure P,. Thus the system would operate continuously to maintain substantially constant pressures in the various chambers and to supply steam to the evaporator at pressure 1 From the foregoing it will beevident that the ducts l to 7 are arranged in the form of loops, the ducts 2 and 3 constituting one loop, ducts 4 and 5 constituting a second loop, and the ducts 6 and 7 constituting a third loop. It will also be obvious that a part of the exhaust steam issuing from evaporator D passes successively through the chambers and C, to the exhaust duct 12 and that a part of the live steam from source S passes successively through chambers Q, and C, to the evaporator D. The steam passing to the evaporator through duct (3 is a mixture of live steam and exhaust steam and by regulating the proportions of live steam and exhaust steam the rate of heat supplied to the evaporator may be varied. It will be apparent from the toregoing and from subsequent descriptions that the number of chambers C,, etc, may be 0 varied to suit different conditions as. for example, ditferent pressures of live steam available, different pressures of exhaust vapor given off by the evaporator, different desired rates of evaporation, etc.

The tendency to superheiit the. steam in the respective chambers is counteracted by the evaporation of the moisture contained in the vapor from the evaporator. This tendency to superheat may be counteracted or regulated by varying the proportion of live steam to exhaust steam, by introducing moisture into the respective chambers. or in any other suitable manner. In starting up the system the desired conditions of steam pressure and steam flow may be established in any suitable manner, as by varying the effective size of the ejector openings, throttling the steam ducts, introducing live steam into the respective chambers at the desired pressure, as will be obvious to persons skilled in the art. It will also be understood that when working below atmospheric pressure the exhaust from the series of chambers would be connected to a condenser, that the air pump of the condenser could be connected directly to each of the various chambers, and that the respective chambers could be provided with such adjuncts aspressure gages, etc.

As illustrated in Fig. 1 the system above described may be employed in multiplex form by passing the exhaust. steam from one set of apparatus to a second set and it desired from the second set to still other sets. 1 Thus in Fig. 1 the duct 12 is connected to the first of a series of steam chambers (7,,

C and C associated with a second evaporator 1),, the chambers being connected together and to the evaporator by means of ducts 13, 14. 15, 16 and 17 in a manner similar to the connections in the right-hand set. with ejectors E, and E, in ducts 15 and 17 respectively. The pressures in the second set of chambers may be regulated as desired but they preferably correspond to the pressures in the firstset of chambers, the pressures in chambers C and being 1 P and P respectively. An exhaust duct l8 leads oti t'rom'chamber C, and this duct may be connected to the first of a third-set ot' chambers C, andtfl. The chamber C, is connected to the inlet 19 and outlet 20 of evaporator-D by ducts 21 and 22, and the chamber C is connected to an ejector E in 195 duct through duct 23, the exhaust duct 24 leading off from chamber 0,. lVhile the pressures in chambers C, and may be regulated as desired they preferably correspond to the pressures in the corresponding her C chambers of the other sets, with a pressure of P in chamber C and a pressure of P in chamber C The steam exhausted through duct 21 is preferably conducted to a condenser. hen employing a plurality of sets of apparatus as shown in Fig. 1 the evaporative eifect of the system may be varied by disconnecting one or more sets of apparatus. Thus a single etfect may be obtained by employing only the right-hand set of apparatus. a double effect may be obtained by employing the right-hand set and the middle set. and a triple etfect may be obtained by employing all three sets. It will be understood that by employing a suitable number of steam chambers in the respective sets any desired number of sets may be employed.

However in accordance with the objects of the present invention I prefer to vary the output in a ditferent manner from that above described in connection with Fig. 1 and in a manner such that only a single set of apparatus is required to obtain either a single. double. triple. etc.. effect. One such method may be performed as illustrated in Figs. :2. 3 and 1. with apparatus similar to the set of apparatus shown at the right-hand end of Fig. 1. comprising a source of live steam S. an evaporator D. ejectors E E and E chambers C and C and steam ducts 1. 2. 3. 1. 6 and 7 connecting the respective chambers together and to the source S and evaporator D. \Vith this single system different evaporative effects may be obtained in the following manner:

To obtain a single effect the system may be adjusted to operate as described in connection with the right-hand set of apparatus in Fjg. 1 whereby one pound of steam at pressure P. will raise one pound of steam at pressure P to pressure P in chamber O one pound of steam at pressureP will raise one pound of steam at pressure P to pressure P in chamber C and one pound of steam at pressure P will raise one pound of steam at pressure P to pressure 1 in cham- Thus the system will continuously. supply steam to the evaporator at the rate of one pound at pressure P per unit of ti1'ne,-during which unit of time one pound of live steam is supplied to the system at pressure P. and one pound of steam is exhausted from chamber C at pressure P through duct 12 (Fig. 2). 12 (Fig. 3) and 12 (Fig. 1).

In order to obtain a double e 'a-porative effect with the single system, steam is exhausted -from chamber C instead of chamber C as illustrated at 12' in Fig. 3, and the ejectors are regulated so that different proportions of live steam and exhaust steam are mixed together in the respective chambers. For example, two pounds of steam issuing from evaporator D at pressure P may be raised to pressure P in chamber C by two pounds of steam issuing from ejector E at pressure P Two of these four pounds of steam are returned to the evaporator through duct 6, while two pounds are fed to chamber C through duct 5. The two pounds of steam passing through duct 5 may be raised from pressure P to pressure P in chamber C by two pounds of steam issuing from ejector E at a pressure P Of the four pounds of steam introduced into chamber C per unit of time, two pounds are fed to ejector E through duct 4: as described, one pound is fed through duct'3 to chamber C and one pound is exhausted through duct. 12. The pound of steam fed to chamber C through duct 3 is raised from pressure P to pressure P by one pound of steam from the source S at pressure P Thus during a single unit of time while one pound, of live steam at pressure P is supplied to the system as in Fig. 2. two pounds of steam, instead of one pound as in Fig. 2. are fed to the evaporator at pressure P and one pound of steam is exhausted at pressure P instead of pressure 1? as in Fig. 2. Thus during the same unit of time twice as much heat is supplied to the evaporator as described in connection with Fig. 2, whereby a double evaporative effect is produced.

To obtain a triple evaporative effect steam is exhausted from chamber C as illustrated in Fig. 1 at '12", and the ejectors are regulated to produce the following proportions of live steam and exhaust steam inthe respective chambers. Three pounds of steam issuing from evaporator D at pressure P are raised to pressure P in chamber C by three pounds of steam issuing from ejector E at pressure P Of the six pounds ofi steam thus supplied to chamber C. at pressure P three pounds are returned to the evaporator through duct 6, two pounds are fed to the chamber C through duct 5 and one pound is exhausted through duct 12 The two pounds of steam passing through duct 5 are raised to pressure P in chamber C by two pounds of steam issuing from ejector E at pressure P Of the four pounds of steam thus supplied to chamber C three pounds are fed to ejector E as described and one pound is fed to chamber C through duct 3. The steam passing through duct 3 is raised from pressure P to pressure P by one pound of steam issuing from ejector E at pressure The two pounds of steam fed to chamber C at pressure P are fed to ejector E as described. Thus, during a single unit. of time while one pound of steam is being supplied to the system at pressure P as in Figs. 2 and 3, three pounds. of steam are being supplied to the evaporator at pressure P instead of two pounds as in Fig. 3 and one pound as in Fig. 1. One pound of steam is exhausted till ' from the source S to the ejector E in Fig. 4 during the unit of time as in Figs.

2 and 3, but from chamber C instead of chamber C in Fig. 3 and chamber C, in Fig. 2. Obviously by employing a larger number of steam chambers a greater number of evaporative effects may be obtained; also, that effects intermediate the single, double, triple, etc., efi'ects may be obtained by employing a greater number of steam chambers or by regulating the ejectors difi'erently.

Another embodiment of my improved method of regulating the evaporative effects in a single evaporator is illustrated in Figs. 6 and 7. According to this method, a single evaporative effect may be obtained by employing a single steam chamber intermediate the source of live steam and the evaporator as illustrated at C in Fig 5, the chamber C being connected. to the evaporator D through the ducts 6 and 7 as in Figs. 2 to 4. Instead of supplying live steam to chamber C, through the medium of charmbers C, and and associated ducts as in Figs. 2 to i, live steam is supplied directly Steam is exhausted from chambers C, through duct 25 The chambers C, and C ejectors E and E and associated ducts which are not used in obtaining a single effect are. shown in dotted lines in Fig. 5, it being understood that to obtain double and tripl effects as hereinafter described these chambers will be provided, but will be cut off from the connections shown in full lines in Fig. 5 in obtaining the single eflcct.

The operation of the system shown in Fig. 5 is as follows: @ne pound of steam exhausted from evaporator B through duct 7 is raised to pressure P, in chamber C by one pound of steam issuing from ejector F, at pressure P 0f the two pounds of steam thus delivered to chamber 6,, one pound is returned to the evaporator through duct 6 and. one pound is exhausted through duct 25. To obtain a double elite ct according to the last. mentioned method, two steam chambers and C may be connected in series as illustrated in full lines in 6, the chamber C being connected to the evaporator by ducts 6 and as before and the chamber C, being connected to the chamber C by ducts a and 5. The ejector E is'supplied with steam through duct 4 and the ejector E, in duct 5 is supplied with steam through ductfl? di* rectly from the source S. The chamber C ejector E and associated ducts are out o'li from the system as indicated by dotted lines. The operation of the system shown in Fig. 6 is as follows: Two pounds of steam issuing from the evaporator at pressure P, are raised to pressure P by two pounds oi: steam issuing from ejector F), at pressure P f the tour pounds of steam thus delivered to chamber C two pounds are returned to the evaporator through duct 6, one pound is delivered to chamber C through duct 5, and one pound is exhausted through duct 25. The pound of steam passing through duct 5 is raised from pressure P, to pressure P by one pound of steam issuing from ejector E, at pressure P The two ounds of steam thus delivered to chamber are both conducted through duct 4 to the ejector E, as described. The pressure and rate of flow of the steam in the various chambers may be controlled by regulating the ejectors or by throttling the ducts as above described in connection with thepreceding methods.

In order to obtaina triple evaporative effect according to the last mentioned method, all of these chambers C C and C are connected in series as illustrated in Fig. 7, the connect-ions in this figure being identical with the connections in Fig. 4: where a triple effect may be obtained as above described. The triple effect obtained according to the last mentioned method by the connection shown in Fig. 7 is preferably obtained in the same manner as hereinbefore described in connection with Fig. 4.

The pressures P P and P in Figs 5 to 7 preferably increase in the order indicated by the sub-scripts so that the pressure P, in the last chamber in Fig. 5 is greater than the pressure P, in the corresponding chamber in Fig. 6, and the pressure P in Fig. 6 is preferably greater than the corresponding pressure P, in Fig. 7. Thus while one pound of steam at pressure P, is supplied to the system during one unit of time in each figure, one pound of steam is being delivered to the evaporator at pressure P, in Fig. .5, two pounds or steam are being delivered to evaporator D at pressure P in Fig. 6, and three pounds of steam are being delivered to evaporator D at pressure P, in Fig. 7. By choosing suitable pressures in the va rious chambers, the rate of evaporation may be varied to any extent by the method illustrated in Figs. 5 to 7. If the pressures P P and P in Fig. 5 were 2, 8, and 32 pounds respectively and if the pressures P P P and P in Fig. 6 were 2, 5, 12% and 32 ipunds respectively and if the pressures P P P, and P in Fig. 7 were 2, 4e, 8, 16 and 32 pounds respectively, the rate of evaporation persquare foot of heatin surface would be greater in Fig. 5 than in *ig. 6, and greater 1n Fig.- 6 than in Fi 7 a A comparison of the two specific embodiments of my im roved method described in connection with igs. 2 to 4: on the one hand and Figs. 5 to 7 on the other hand will indicate that in the former method the same number ofsteani chambers are employed in obtaining the different evaporative effects while in the latter method a variable number of steam chambers are employed; that in the former 1 method the same number of ejectors are employed in obtaining the various effects while in the latter method a variable number of ejectors are employed; that the steam is exhausted from different chambers according to the former method and from the same chamber according to the latter method; that the pressure in the evaporator preferably remains constant in the first method, while it varies in pressure in the latter method; and that the ejectors are preferably varied in size in both methods. However, it is to be understood, that the exhaust steam may be exhausted from different chambers in the latter method as in the former method; that the pressure in the evaporator may be varied in the former method as in the latter method; that the pressure of the steam delivered to the evaporat r may be maintained constant in the latter method as in the former method; and that other variations may be made within the scope of the present invention as defined by the appended claims.

As hereinbefore stated the pressures in the steam chambers may be regulated as desired to meet different conditions of operation. However, the following considerations should be borne in mind in connection with the application of the invention to evaporator systems.

In controlling the evaporative effect by operating a battery of evaporators in series, with the first evaporator exhausting to the second evaporator and so on, as hereinbefore stated to be a common practice, and as commonly involving evaporating vessels of large diameter and a limited temperature range, the range of temperature is divided between the respective evaporators of' the battery. Thus, when employing two evaporators of a battery to obtain a double effect the temperature range is divided substantially by two, when employing three evaporators to obtain a triple effect thetemperature range is divided substantially by three, etc. Thus in order to obtain the desired output with a multiple or battery system the heating surface of each evaporator must be made disproportionately large to ofiset the limited temperature range available therein. In varying the evaporative effect in a single evaporator according to the present invention the ran'geof temperature is not divided between a series of evaporators and consequently a greater output is available with a predetermined amount of heating surface or conversely less heating surface is required for a predetermined maximum output.

Ihave described the present invention with particular reference to a system for manufacturing salt but it will be understood that the invention, in certain of its aspects, is applicable to systems for manufacturlng sugar, soap, glycerin, etc., which employ evaporative processes; and that it is applicable to steam power plants and other steam systems in which the exhaust steam is capable of being re-utilized. It will therefore be understood that the references in the specification and claims to the manufacture of salt are employed in an illustrative sense and not in a definitive sense. The term live steam is employed herein to designate steam at a pressure higher than the pressure of the exhaust steam which is reutilized and is therefore employed merely in contradistinction to exhaust steam. The term exhaust steam is intended to cover either steam or vapor, and it is also intended to cover any kind of vapor whether water vapor or other vapor. I have herein referred to steam chambers as distinct elements but the chambers may if desired be constituted by portions of the steam ducts as illustrated in Fig. 7 where the horizontal port-ions of the ducts constitute the steam chambers.

'I claim:

1. In a system of the character described the combination of a steam-operated device having a steam inlet through which steam may be supplied thereto and having a steam outlet through which steam may be exhausted therefrom, a steam duct connecting said outlet with said inlet so that exhaust steam issuing from said outlet may be returned through said inlet, a steam ejector in said duct for raising the pressure of the exhaust steam, a second steam duct connecting said ejector with said first duct at a point in advance of said ejector so that steam may be supplied from said first duct to said ejector after having been raised in pressure by said ejector, a second steam ejector in said second duct for raising the pressure of the steam in said second duct in transit from said first duct to said first ejector, and means for supplying steam to said second ejector at a pressure higher than the pressure in said second duct in the rear of said second ejector.

2. In a system of the character described the combination of a source of steam, a steam-operated device having a steam inlet through which steam may be supplied thereto and having a steam outlet through which steam may be exhausted therefrom, a series of steam loops interposedbetween said source and said device, the ejector in the first loop being connected to said source 'of steam, the last loop beingconnected at its opposite ends to said. inlet and said outlet, and each intermediate loop being connected at one end to the ejector in the next succeeding loop and at its other end to the next succeeding loop at a point in advance of the ejector therein.

3'. In a system of the character described for manufacturing salt and the like, the

combination of a source of live steam, an evaporator, a plurality of intermediate chambers. steam ducts connecting said source,'evaporator and chambers together so I that exhaust steam is conducted through said chambers successively in one direction and live steam is conducted successively through said chambers in the other direction, and ejectors for ejecting the steam from each chamber into the steam entering the next chamber of lower pressure so as to raise the pressure of the steam entering the next chamber of lower pressure, said ducts including a duct for feeding steam from one of said chambers to said evaporator.

4. In a system of the character described the combination of a source of live steam, a steam-operated device having a steam inlet and a steam outlet, a series of steam chambers intermediate said source and said device, a steam conduit leading from each chamber to the next preceding chamber, a steam conduit leading from said outlet to the last chamber, an ejector in each of said conduits, a steam duct leading from said source to the ejector in the first of said conduits, a steam duct leading from each of said chambers except the last chamber to the ejector in the conduit leading to the next succeeding chamber, and a steam duct leading from the last chamber to said inlet.

5. In the manufacture of salt and the like by evaporation in a'closed evaporator, the

method of effecting the evaporation comprising supplying live steam in one direction through aseries of steam loops to the evaporator, exhausting steam from the evaporator through said series of loops in the other direction, successively raising the pressure of the exhaust steam in transit through said loops by means of said live steam, at the same time reducing the pressure of the live steam in transit to the evaporator, and conducting a'portion of the exhaust steam back to the evaporator after having been raised in pressure as aforesaid.

6. In the manufacture of salt and the like by evaporation in a closed evaporator, the method of effecting the evaporation comprising supplying live steam in one direction through a series of steam loops to the evaporator, exhausting steam from the evaporator through said series of loops in the other direction, successively raising the pressure of the exhaust steam in transit through said loops by means of said live steam, at

the same time reducing the pressure of the live steam in transit to the evaporator, and regulating the exhaust steam returned to the evaporator soras to control the amount of exhaust heat returned to the evaporator.

7. In the manufacture of salt and the like by evaporation in a closed evaporator, the method of effecting the evaporation comprising supplying live steam in one direction through a series of steam loops to the evaporator, exhausting steam from the evaporator through said series of loops in the other direction, successively raising the pressure'of the exhaust steam in transit through said loops by means of said live steam, at the same time reducing the pressure of the live steam in transit to the evaporator, and regulating the amount of exhaust steam returned to the evaporator so as to control the amount of exhaust heat returned to the evaporator.

8. In the manufacture of salt and the like by evaporation in a closed evaporator, the method of effecting the evaporation comprising supplying live steam in one direction through a series of steam loops to the evaporator. exhausting steam from the evaporator through said series of loops in the other direction, successively raising the .pressure of the exhaust steam in transit through said loops by means of said live steam. at the same time reducing the pressure of the live steam in transit to the evaporator, and regulating the pressure of the exhaust steam returned to the evaporator so as to control the amount of exhaust steam returned to the evaporator.

9. In the manufacture of salt and the like byevaporation in a closed evaporator,.the method of effecting the evaporation comprising supplying live steam in one direction through a seriesof steam loops to the evaporator, exhausting steam from the evaporator through said series of loops in the other direction, successively raising the pressure of the exhaust steam in transit through said loops by means of said live steam, at the same time reducing the pressure of the live steam in transit tothe evaporator, and regulating both the pressure and the amount of the exhaust steam returned to the evaporator so as to control the amount of exhaust heat returned to the evaporator.

'10. In manufacturing salt and the like by evaporation in a closed evaporator, where live steam is available at a relatively high pressure and exhaust steam is produced in the evaporator at a lower, pressure, the method of controlling the evaporation comprising passing the live steam and exhaust steam in opposite directions through .a series of steam loops so as progressively to lower the pressure of the live steam in one direction and progressively to raise the pressure of the exhaust steam in the other direction in a plurality of stages. and feeding steam to the evaporator from one of said stages at a pressure intermediate the pressures of the live steam and exhaust steam.

11. In manufacturing salt and the like by evaporation in a closedevaporator where live steam is available at a relatively high method of controlling the evaporation comprising passing the live steam and exhaust steam in opposite directions through a series of steam loops so as progressively to lower the pressure of the live steam in one direction and progressively to raise the pressure of the exhaust steam in the other direction in a plurality of stages, and regulating said intermediate stages so as to control the pressure of the steam fed to the evaporator.

12. In manufacturing salt and the like by evaporation in a closed evaporator, where live steam is available at a relatively high pressure and exhaust steam is produced in the evaporation comprising passing the live steam and exhaust steam in opposite directions through a series of steam loops so as progressively to lower the pressure of the live steam in one direction and progressively to raise the pressure of the exhaust steam in the other direction in a plurality of stages, and regulating the number of said intermediate stages so as to control the pressure of the steam fed to the evaporator.

13. In manufacturing salt and the like by evaporation in a closed evaporator, where live steam is available at a relatively high pressure and exhaust steam is produced in the evaporator at a lower pressure, the method of controlling the evaporation comprising passing the live steam and exhaust steam in opposite directions through a series of steam loops so as progressively to lower the pressure of the live steam in one direction and progressivelyto raise the pressure of the exhaust steam in the other direction in a plurality of stages, andregulating the pressure in said intermediate stages so as to control the pressure of the steam fed to the evaporator. A r ,7 f

14. In manufacturing salt and the like by evaporation in a closed evaporator, where live steam is available at a relatively high pressure and exhaust steam is produced in the evaporator at a lower pressure, the method of controlling the evaporation comprising passing the live steam and exhaust steam in opposite directions through a series of steam loops so as progressively to lower the pressure of the live steam in one direction and progressively to raise the pressure of the exhaust steam in the other direction in a plurality of stages, and regulating both the number of said intermediate stages and the pressures in the stages so as to control the pressure of the steam fed to the evaporator.

15. In manufacturing salt and the like by evaporation in a closed evaporator, where live steam is available at a relatively high pressure and exhaust steam is produced in the evaporator at a lower pressure, the method of controlling the evaporation comprising passin the exhaust steam in one di-- rection througi a series of steam chambers, passing the live steam through the series of chambers in the other direct-ion, progressively raising the pressure of the steam in the succesive chambers in the first direction by ejecting steam from the next chamber of higher pressure thereinto, and feeding steam from one of said chambers to the evaporator.

Signed by me at Port Huron, Michigan, this thirteenth day of November, 1918.

CHARLES LEWIS WEIL. 

